I think it's important to remember that "good, quality posts" is at least somewhat subjective. People can disagree on what constitutes "good, quality posts".

I'll freely admit I posrepped some fairly controversial posts. But in my view, an atypical viewpoint, even if a bit more strongly worded than what's ideal, can add a lot to discussion. I agree with what Gooral wrote about the value of having a wide difference of opinion on threads, so when I saw someone take a bold and controversial stand, I'd often feel compelled to give a "pat on the back" to the person doing that.

I'll also freely admit that there are particular posters that I came back to a lot in posrepping them. But this was almost always because I truly did appreciate the post that I was posrepping, or wanting to thank that person for posrepping me. It's not purely because many of these people are my friends.

Finally, I'll admit I went on at least two or three "posrep runs" in the past because I wanted to posrep a particular member that I was not yet in a position to posrep again (this was often due to that member making a great avatar or sig for me, IIRC). During these posrep runs I would search for posts that I felt were good, or witty, or at least had something to them that I liked.

Ultimately, I tended to view posrep as benign, and not really something that could be abused. Perhaps I was wrong there, as board-wide power creep wasn't something I gave a lot of thought to, admittedly.